A cuvette is a container, transparent in at least one direction at wavelengths of interest for a particular spectrometric measurement. Such containers are routinely employed in optical spectrometry, such as in the application of absorption spectrometry.
One common design for a cuvette is a square prism, open at one end to allow admission and removal of liquid specimens. At least two opposite sides of the prism are transparent, optically flat, and slightly wedged so that the device does not act as a Fabry Perot interferometer. All four rectangular walls may optionally be transparent. Commonly, the non-transparent walls are translucent rather than opaque. While a geometry in which the cuvette is 4.5 cm tall with inside cross section a 1.0 cm square, cross sections from 1 mm (parallel to the light path) by 1 cm to 10 cm (parallel to the light path) by 1 cm are common. Another common design is a cylinder with a side port allowing admission and removal of liquid specimens. In this case, the end caps of the cylinder are transparent and optically flat.
Many materials have been used for such cuvettes, with glass, quartz, polystyrene, polycarbonate, and polymethylmethacrylate widely available. Among other uses, such cuvettes are placed in the light beam of a spectrometer, photometer, colorimeter, or spectrophotometer so that liquids inside the cuvette may be assayed for light transmission or absorption, which are indirect measures of chemical concentration.
If not observed without modification, the light passed through such a cuvette is typically dispersed by a grating or prism, observed with an interferometer, or attenuated with a filter prior to detection. Such modification of the light beam allows selection of those wavelengths or frequencies of light most useful to a particular measurement purpose. A key point is that separation of light into its component colors, wavelengths, or frequencies is carried out separately from the cuvette or container. An exception to this separation of containing sample and separating wavelengths was disclosed in U.S. Pat. No. 8,885,161. Among the embodiments of that patent was the use of a disposable/single use cuvette onto one face of which two or more mutually-rotated diffraction gratings were attached. Importantly, the gratings were in close proximity to each other, effectively adjacent and in or about in contact with each other. This configuration generates a number of cylindrically-arranged multiple diffraction orders, such that dispersion is cylindrically-symmetrical.